1. Field of the Invention
This invention relates to a temperature scanner for detecting the temperatures or relative temperatures of positions on the surface of a hot steel strip moving relative to said scanner and in particular to analysis and display means used in such a scanner.
2. Description of the Prior Art
Temperature scanners of this kind have many applications but are particularly useful in steel rolling mills. In a hot steel strip rolling mill for example a hot steel strip is progressively lengthened and reduced in thickness by being passed through a train of rolling stands. The hotter the steel is, the more ductile it becomes. This however, leads to the disadvantage that an uneven temperature distribution over the strip will result in some portions being lengthened and reduced in thickness to a greater extent than other portions. In a rolling mill where high speeds are achieved by the strip as a result of its being lengthened, such uneven elongation can result in dangerous buckling or deviation of the strip from its intended path. Even if the uneven treatment is not sufficient to cause an accident the quality of the strip will be adversely affected by damage to the strip edges, caused by the strip scraping against stops on the strip table.
It is therefore very desirable to have a readily accessible and understandable means of assessing the temperature distribution over a strip passing through such a mill so that action may be taken to prevent any uneveness in the temperature distribution. It would also be desirable to have a ready means of continuously determining whether such a strip was correctly aligned in the mill and to be able to continuously measure the strip width during rolling.
Various infra-red temperature scanners have been proposed in the past. FR 2397627 discloses an infra-red pyrometer and mirror for scanning the temperature of the output of a sintering plant. The information desired is displayed solely as temperature profiles. The device disclosed is first of all unsuitable for use in a hot steel strip rolling mill for several reasons. A sintering line has a very low speed in contrast to a hot strip mill, the device is not suitable for accurately measuring temperatures between 800.degree. and 1000.degree. C. as encountered in a hot strip mill and furthermore the device cannot determine the temperature of a fast moving hot steel strip having an emission coefficient of 0.8. In addition a sintering line is confined by vertical walls and the device is incapable of determining the width of a steel strip. Secondly and more importantly the display of the information collected by the infra-red scanner can only be present as temperature profiles which thus severely limits the ease of comprehension and choice as to the most convenient form of presentation for the operator.
U.S. Pat. No. 3,736,375 again uses infra-red pyrometry but in this case uses it to study a ribbon of glass. This too is relatively slow moving and again only enables one form of presentation to be used. This is in the form of a temperature contour chart incorporating a reference contour and a median contour. However the device is unsuitable for use with a hot steel strip rolling mill in which the steel strip moves considerably faster. Furthermore the lack of choice concerning the display mode again severely limits the case of comprehension and choice as to the most convenient form of presentation for the operator.
In the past the use of infra red sensors has been proposed to monitor the temperature of a steel strip (DT-AS 2349611). However the information derived by such sensors has been used directly to control the rolling stands, and no readily accessible and understandable means of analysing the output obtained by such a sensor and making it directly available to an operator has been proposed.